When preparing to make a dental replacement or to carry out orthodontic measures or various restorative measures, it is necessary to take an impression of individual teeth, a number of teeth or the whole jaw. For this purpose, impression trays are used which are made of metal or a hard plastic and are filled with an elastomeric impression compound. When taking the impression, the tray encloses the tooth or teeth in an approximate U-shape and thus presses the impression compound onto the jaw area of which an impression is required.
Existing dental impression trays make it possible to take an impression of two opposite jaw sides in one operation. Examples of such existing trays are disclosed in U.S. Pat. Nos. 4,689,010 and 5,513,985. These trays have side walls which are adapted to the shape of the jaw and which are designed in such a way that, when the impression is being taken, they at least partially enclose the sides of the teeth of which an impression is required, both in the upper jaw and in the lower jaw regions. Approximately at half the height of these side walls, a flexible mesh-like layer is fixed between them. The tray is filled on both sides with an elastomeric impression compound and can thus be used for simultaneously taking an impression of the opposite jaw sides.
In principle, by allowing for the simultaneous impression taking of the upper and lower jaws, these trays permit a more accurate recording of the situation for partial or complete bite replacements. In particular, they permit registration of the counterbite, which is important for a bite replacement. In practice, however, the use of such trays is associated with problems. For reasons related to its construction (e.g., the layer that extends between the side walls comprises a non-rigid mesh-like material), existing dental impression trays are not sufficiently rigid.
When taking the impression, and in particular when removing the finished impression from the mouth, the dental impression tray can deform, so that the finished impression no longer corresponds to the conditions in the mouth. In particular, removal from the mouth can be problematic because hardened impression material often adheres to teeth with great force. Moreover, when taking the impression, there is a possibility that the bite will go as far as the flexible mesh-like layer of the tray, or may even bite completely through this, so that teeth of the upper jaw and lower jaw come into direct contact with one another and it is no longer possible to obtain an exact impression of the situation.